Various embodiments relate to the problem whereby, in operating devices with an SELV (Safety Extra Low Voltage) output, the tangible voltage at the output must not exceed a predefinable voltage, for example 60 V, when there is a fault. This should be ensured by means of appropriate protective circuitry.
The prior art discloses the practice of connecting an appropriate protective apparatus on the secondary side using hardware and of passing an appropriate item of information, by means of optocouplers, to the drive apparatus which then switches off the circuit arrangement. Alternatively, it is known practice to measure the value of the output voltage and to transmit this value to the drive apparatus via an optocoupler, the drive apparatus being designed to cause the circuit arrangement to be switched off when the measured value of the output voltage exceeds a predefinable value.
The disadvantage of these known procedures is the fact that both require an optocoupler. The cost associated with the use of an optocoupler is undesirably high for certain fields of application of such circuit arrangements, in particular if LEDs are used as the luminous means.